Method for efficiently synthesizing epichlorohydrin

Abstract

The invention relates to the technical field of chemical production, in particular to a method for efficiently synthesizing epichlorohydrin. The method provided by the invention comprises the following steps: adding a mixed solution of chloropropene and methanol and part of hydrogen peroxide into a reactor; then injecting residual hydrogen peroxide through a middle-section feeding hole of the reactor; constant-temperature circulating water is adopted to control a front-section temperature control area of the reactor to be at a first temperature, a middle-section temperature control area of the reactor to be at a second temperature and a rear-section temperature control area of the reactor to be at a third temperature, and the third temperature, the first temperature and the second temperature are gradually increased in sequence. The method provided by the invention can effectively solve the problems of side reaction increase, too fast catalyst deactivation and the like caused by local overheating of the fixed bed reactor, and significantly improves product selectivity and production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and in particular to a method for efficiently synthesizing epichlorohydrin. Background Art

[0002] Epichlorohydrin is an important organic intermediate widely used in epoxy resins, epichlorohydrin rubber, plasticizers, and other fields. Current industrial production primarily utilizes high-temperature chlorination of propylene, the propylene acetate method, and the chlorination of glycerol. However, these traditional processes all require a dichloropropane saponification step, resulting in high energy consumption, high pollution levels, and the generation of large amounts of chlorine-containing wastewater and residue.

[0003] Direct epoxidation of allyl chloride using titanium silicalite as a catalyst is considered a promising green synthesis route due to its low energy consumption and environmental friendliness. If this process can achieve industrialization, it is expected to become the mainstream technology for epichlorohydrin production in the future.

[0004] Invention publication number CN111072598A discloses a process for producing epichlorohydrin by direct oxidation using a titanium silicalite catalyst. The specific steps are: a methanol catalyst mixture and fresh allyl chloride are pumped into a first mixer via a metering pump, mixed with hydrogen peroxide, and then reacted in a first tubular reactor; the reaction product undergoes gas-liquid separation, the liquid phase is mixed with supplemental hydrogen peroxide in a second mixer, and then reacted in a second tubular reactor; the reaction product undergoes further gas-liquid separation and enters a separation tank to separate the solid catalyst and liquid product; the catalyst slurry is returned to the batching tank for recycling, and the liquid product is recovered through an upper filter. This method features a high epichlorohydrin yield and efficient hydrogen peroxide utilization. Invention publication number CN117510438A discloses an apparatus for epoxidation and a method for producing epichlorohydrin. The method comprises: introducing a reaction feed into a reactor, allowing it to react with a catalyst, mixing the product with an inert gas, and performing gas-liquid separation; when the pressure at the reactor's lower end exceeds an alarm value of 2 MPa, stopping the feed and performing a reverse backwash for at least 1 second, with the backwashed material discharged from the lower end; and then repeating the above steps. This device and method effectively control the reactor inlet pressure within a safe range and significantly prolong the epoxidation reaction time. The direct epoxidation of allyl chloride in industrial production typically utilizes a fixed-bed reactor. This process offers significant catalytic activity and high selectivity, efficiently converting allyl chloride and hydrogen peroxide into the target product, epichlorohydrin. However, the epoxidation reaction is a highly exothermic process, with reaction heat concentrated in the catalyst bed, particularly in the mid-reactor region, which can easily form localized high-temperature zones (temperatures exceeding 60°C). This localized overheating not only accelerates catalyst deactivation and shortens its service life, but also triggers side reactions such as over-oxidation and ring-opening reactions, leading to increased byproduct formation. This significantly reduces the selectivity and overall yield of the target product, directly impacting the economic and sustainable nature of production. Summary of the Invention

[0005] To address the aforementioned technical issues, the present invention provides a reactor temperature control process for the direct epoxidation of allyl chloride to produce epichlorohydrin. This process is particularly suitable for suppressing localized overheating and improving production efficiency in fixed-bed reactors. Through staged cooling and multi-stage feed optimization, the present invention achieves precise temperature control of the fixed-bed reactor in the direct epoxidation of allyl chloride, addressing the increased side reactions and catalyst deactivation caused by localized overheating, while also improving production continuity and energy efficiency.

[0006] Specifically, the present invention provides a method for efficiently synthesizing epichlorohydrin, comprising: 1) A mixture of allyl chloride and methanol and a portion of hydrogen peroxide are added to a reactor; then the remaining hydrogen peroxide is injected through the feed port in the middle section of the reactor.

[0007] 2) Constant temperature circulating water is used to control the front temperature control zone of the reactor to the first temperature, the middle temperature control zone to the second temperature, and the rear temperature control zone to the third temperature, and the third temperature, the first temperature, and the second temperature increase in sequence. In the present invention, hydrogen peroxide is divided into the main feed (added all at once) and the supplementary feed (slowly injected in the middle section), and the concentration of the reactants is controlled in stages to achieve a gradient release of the reaction heat. The fixed-bed reactor is divided into three independent temperature-controlled zones: the front section (preheating zone), the middle section (main reaction zone), and the rear section (stabilization zone). The temperature of each zone is differentially adjusted by constant temperature circulating water to ensure the stability of the catalyst surface temperature and avoid local overheating. The continuous production process of epichlorohydrin based on segmented cooling and multi-stage feed optimization effectively solves the problems of increased side reactions and rapid catalyst deactivation caused by local overheating of the fixed-bed reactor through innovative temperature control methods and feeding strategies, and significantly improves product selectivity and production efficiency.

[0008] Preferably, in step 1), the molar ratio of allyl chloride to methanol is 1:5-20, preferably 1:10-15, for example, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc.

[0009] Preferably, in step 1), the molar ratio of hydrogen peroxide to allyl chloride is 1:0.5-5, preferably 1:1-2, and more preferably 1:1.5-1:1.9, for example, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, etc. Using the above raw materials in the preferred ratio can better solve the above-mentioned problems and improve selectivity and catalyst life.

[0010] Preferably, in step 1), the proportion of the partial hydrogen peroxide to the total hydrogen peroxide is 50% to 90%, preferably 70% to 80%, for example, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, etc.

[0011] More preferably, the mass concentration of the hydrogen peroxide is 30% to 50%. In the present invention, there is no special requirement for the concentration of the hydrogen peroxide. For the present invention, the mass concentration of the hydrogen peroxide is preferably 30% to 50%, for example, 30%, 35%, 40%, 45%, 50%, etc.

[0012] In the present invention, a reaction environment with a progressive concentration gradient is formed by the operation of staged feeding, reaction heat is released in stages, the instantaneous heat release intensity is reduced and the generation of hot spots is suppressed. When the ratio of allyl chloride, methanol and hydrogen peroxide is optimized, the above-mentioned staged feeding method can form a better progressive concentration gradient effect.

[0013] Preferably, in step 2), the front temperature-controlled zone is the inlet zone, and the first temperature is 35-40°C to better preheat the reactants, such as 35°C, 36°C, 37°C, 38°C, 39°C, etc., preferably 35-38°C.

[0014] Preferably, in step 2), the middle temperature-controlled zone serves as the main reaction zone, and the second temperature is 30-35°C to better balance the reaction heat and suppress the formation of hot spots. Examples include 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, etc. Preferably, the temperature is 30-34°C.

[0015] Preferably, in step 2), the latter temperature-controlled zone is a stabilization zone, and the third temperature is 40-45°C to better stabilize the product yield, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, etc. Preferably, it is 40-44°C.

[0016] In the present invention, the operation of the zoned temperature-controlled epoxidation reaction strengthens heat removal by controlling the low temperature of the main reaction zone, stabilizes the catalyst surface temperature at 40-45°C, suppresses heat accumulation, and achieves better results by optimizing the first to third temperatures, which can significantly improve epichlorohydrin selectivity and catalyst service life.

[0017] Preferably, in step 2), the fixed bed reactor is filled with a titanium silicate molecular sieve granular catalyst.

[0018] Further preferably, the titanium silicalite granular catalyst has an MFI structure and a particle size of 0.1 to 10 mm, preferably 1 to 3 mm. Combining the titanium silicalite-filled granular catalyst with a continuous epichlorohydrin production process based on staged cooling and multi-stage feed optimization enables better reaction heat control, extends catalyst life, and improves epichlorohydrin selectivity and synthesis efficiency.

[0019] More preferably, in step 2), the temperature is cooled to 10-30°C, preferably 15-20°C after the reaction.

[0020] The present invention provides at least the following beneficial effects: The method for producing epichlorohydrin of the present application divides the fixed-bed reactor into three independent temperature-controlled zones: the front section, the middle section, and the back section, and employs gradient temperature control in each of these zones. This effectively disperses the accumulated heat of reaction, stabilizes the catalyst surface temperature at a suitable level, and significantly suppresses the formation of localized high-temperature zones. Hydrogen peroxide is injected in stages, creating a reaction environment with a progressive concentration gradient, releasing reaction heat in stages and reducing the intensity of transient heat release. The synergistic effect of zoned temperature control and staged feeding addresses the problems of increased side reactions and rapid catalyst deactivation during the reaction, thereby improving the operational stability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic structural diagram of a process for efficiently producing epichlorohydrin provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0024] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0025] Where specific techniques or conditions are not specified in the examples of the present invention, the techniques or conditions described in the literature in the field or in the product specifications were followed. All devices, instruments, reagents, etc. used, where the manufacturer is not specified, are conventional products available through regular channels. All experimental reagents and raw materials involved are commercially available, and all reagents are analytically pure.

[0026] Example 1 This embodiment provides a method for efficiently producing epichlorohydrin. Figure 1 The specific steps are as follows: 1) A mixture of allyl chloride and methanol at a molar ratio of 1:12 and 75% of hydrogen peroxide were added to a reactor; then the remaining 25% of hydrogen peroxide was injected through the feed port in the middle section of the reactor; the molar ratio of hydrogen peroxide to allyl chloride was 1:1.5; and the mass concentration of hydrogen peroxide was 30%.

[0027] 2) Constant temperature circulating water is used to control the reactor's front temperature control zone to the first temperature, the middle temperature control zone to the second temperature, and the rear temperature control zone to the third temperature. The fixed bed reactor is filled with MFI structure titanium silicalite granular catalyst with a particle size of 1.2mm~1.4mm; constant temperature circulating water is used to control the reactor bed temperature. The first temperature is 38°C to preheat the reactants; the second temperature is 32°C to balance the reaction heat and suppress hotspot formation; and the third temperature is 43°C to stabilize product yield. Constant-temperature circulating water is used to differentially adjust the temperature of each zone to ensure a stable catalyst surface temperature and avoid local overheating. The continuous epichlorohydrin production process, based on segmented cooling and multi-stage feed optimization, effectively addresses issues such as increased side reactions and rapid catalyst deactivation caused by local overheating in the fixed-bed reactor through innovative temperature control methods and feed strategies, significantly improving product selectivity and production efficiency.

[0028] The method for efficiently producing epichlorohydrin described in Example 1 effectively addressed the increased side reactions caused by local overheating in the fixed-bed reactor and the problem of rapid catalyst deactivation. The hydrogen peroxide conversion rate reached over 96.0%, the epichlorohydrin selectivity reached over 96.0%, and the catalyst service life reached approximately 200 hours.

[0029] Example 2 This embodiment provides a method for efficiently producing epichlorohydrin. Figure 1 The specific steps are as follows: 1) A mixture of allyl chloride and methanol at a molar ratio of 1:12 and 75% of hydrogen peroxide were added to a reactor; then the remaining 25% of hydrogen peroxide was injected through the feed port in the middle section of the reactor; the molar ratio of hydrogen peroxide to allyl chloride was 1:1.5; and the mass concentration of hydrogen peroxide was 30%.

[0030] 2) Constant temperature circulating water is used to control the reactor's front temperature control zone to the first temperature, the middle temperature control zone to the second temperature, and the rear temperature control zone to the third temperature. The fixed-bed reactor is filled with a granular catalyst of MFI-structured titanium silicalite, with a particle size of 1.2mm-1.4mm. Constant temperature circulating water is used to control the reactor bed temperature, with the first temperature being 35°C to preheat the reactants; the second temperature being 30°C to balance the reaction heat and suppress hot spot formation; and the third temperature being 40°C to stabilize the product yield. Constant temperature circulating water is used to differentially adjust the temperature of each zone to ensure a stable catalyst surface temperature and avoid local overheating. The continuous production process for epichlorohydrin based on segmented cooling and multi-stage feed optimization effectively solves the problems of increased side reactions and rapid catalyst deactivation caused by local overheating in the fixed-bed reactor through innovative temperature control methods and feed strategies, significantly improving product selectivity and production efficiency.

[0031] The method for efficiently producing epichlorohydrin according to Example 2 effectively addressed the increased side reactions caused by local overheating in the fixed-bed reactor and the problem of rapid catalyst deactivation. The hydrogen peroxide conversion rate reached approximately 92.0%, the epichlorohydrin selectivity reached approximately 97.0%, and the catalyst service life reached approximately 250 hours.

[0032] Example 3 1) A mixture of allyl chloride and methanol at a molar ratio of 1:12 and 75% of hydrogen peroxide were added to a reactor; then the remaining 25% of hydrogen peroxide was injected through the feed port in the middle section of the reactor; the molar ratio of hydrogen peroxide to allyl chloride was 1:1.5; and the mass concentration of hydrogen peroxide was 30%.

[0033] 2) Constant temperature circulating water is used to control the reactor's front temperature control zone to the first temperature, the middle temperature control zone to the second temperature, and the rear temperature control zone to the third temperature. The fixed-bed reactor is filled with a granular catalyst of MFI-structured titanium silicalite with a particle size of 1.2mm-1.4mm. Constant temperature circulating water is used to control the reactor bed temperature. The first temperature is 40°C to preheat the reactants; the second temperature is 35°C to balance the reaction heat and suppress the formation of hot spots; and the third temperature is 45°C to stabilize the product yield. Constant temperature circulating water is used to differentially adjust the temperature of each zone to ensure the stability of the catalyst surface temperature and avoid local overheating. The continuous production process of epichlorohydrin based on segmented cooling and multi-stage feed optimization effectively solves the problems of increased side reactions and rapid catalyst deactivation caused by local overheating in the fixed-bed reactor through innovative temperature control methods and feed strategies, significantly improving product selectivity and production efficiency.

[0034] The method for efficiently producing epichlorohydrin according to Example 2 effectively addressed the increased side reactions caused by local overheating in the fixed-bed reactor and the problem of rapid catalyst deactivation. The hydrogen peroxide conversion rate reached approximately 98.0%, the epichlorohydrin selectivity reached approximately 92.0%, and the catalyst service life reached approximately 150 hours.

[0035] Example 4 1) A mixture of allyl chloride and methanol in a molar ratio of 1:12 and 75% of hydrogen peroxide were added to a reactor; then the remaining 25% of hydrogen peroxide was injected through the feed port in the middle section of the reactor; the molar ratio of hydrogen peroxide to allyl chloride was 1:2; and the mass concentration of hydrogen peroxide was 30%.

[0036] 2) Constant temperature circulating water is used to control the reactor's front temperature control zone to the first temperature, the middle temperature control zone to the second temperature, and the rear temperature control zone to the third temperature. The fixed-bed reactor is filled with a granular catalyst of MFI-structured titanium silicalite, with a particle size of 1.2mm~1.4mm. Constant temperature circulating water is used to control the reactor bed temperature, with the first temperature being 38°C to preheat the reactants; the second temperature being 32°C to balance the reaction heat and suppress hot spot formation; and the third temperature being 43°C to stabilize the product yield. Constant temperature circulating water is used to differentially adjust the temperature of each zone to ensure a stable catalyst surface temperature and avoid local overheating. The continuous production process of epichlorohydrin based on segmented cooling and multi-stage feed optimization effectively solves the problems of increased side reactions and rapid catalyst deactivation caused by local overheating in the fixed-bed reactor through innovative temperature control methods and feed strategies, significantly improving product selectivity and production efficiency.

[0037] The method for efficiently producing epichlorohydrin described in Example 1 effectively addressed the increased side reactions caused by local overheating in the fixed-bed reactor and the problem of rapid catalyst deactivation. The hydrogen peroxide conversion rate reached approximately 98.0%, the epichlorohydrin selectivity reached approximately 94.0%, and the catalyst service life reached approximately 150 hours.

[0038] Comparative Example 1 This comparative example adopts the traditional process for producing epichlorohydrin, and the specific steps are as follows: 1) A mixture of allyl chloride and methanol in a molar ratio of 1:12 and all of the hydrogen peroxide were added to a reactor; the molar ratio of hydrogen peroxide to allyl chloride was 1:1.5; and the mass concentration of hydrogen peroxide was 30%.

[0039] 2) Constant temperature circulating water is used to control the temperature of the fixed bed reactor at 40°C. The fixed bed reactor is filled with a granular catalyst of MFI structured titanium silicalite with a particle size of 1.2 mm to 1.4 mm.

[0040] Using the method in this comparative example, the fixed-bed reactor can locally overheat to temperatures exceeding 60°C, leading to increased side reactions and rapid catalyst deactivation. The hydrogen peroxide conversion rate reached approximately 95.0%, while the epichlorohydrin selectivity only reached approximately 90.0%, resulting in a catalyst life of only about 100 hours.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for efficiently synthesizing epichlorohydrin, characterized in that: include: 1) Adding a mixture of allyl chloride and methanol and a portion of hydrogen peroxide to a reactor; then injecting the remaining hydrogen peroxide through the feed port in the middle section of the reactor; 2) Constant temperature circulating water is used to control the front temperature control zone of the reactor to a first temperature, the middle temperature control zone to a second temperature, and the rear temperature control zone to a third temperature, wherein the third temperature, the first temperature, and the second temperature increase in sequence.

2. The method according to claim 1, characterized in that In step 1), the molar ratio of allyl chloride to methanol is 1:5-20, preferably 1:10-15.

3. The method according to claim 2, characterized in that In step 1), the molar ratio of hydrogen peroxide to allyl chloride is 1:0.5-5, preferably 1:1.5-2.

4. The method according to claim 3, characterized in that In step 1), the proportion of the partial hydrogen peroxide to the total hydrogen peroxide is 50% to 90%, preferably 70% to 80%.

5. The method according to any one of claims 1 to 4, characterized in that In step 2), the front temperature control zone is the entrance zone, and the first temperature is 35-40°C.

6. The method according to any one of claims 1 to 5, characterized in that In step 2), the middle temperature-controlled zone is the main reaction zone, and the second temperature is 30-35°C.

7. The method according to any one of claims 1 to 6, characterized in that In step 2), the rear temperature control zone is a stable zone, and the third temperature is 40-45°C.

8. The method according to claim 7, characterized in that In step 2), the fixed bed reactor is filled with a titanium silicate molecular sieve catalyst particle.

9. The method according to claim 8, characterized in that The titanium silicate molecular sieve particle catalyst has an MFI structure and a particle size of 0.1 to 10 mm, preferably 1 to 3 mm.

10. The method according to any one of claims 1 to 9, characterized in that In step 2), the reaction is followed by cooling to 10-30°C, preferably 15-20°C.

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